Jump to content
SAU Community

Recommended Posts

well you mentioned the manual so youve probabaly allready read this but anyway

Standard is 171psi at 300rpm

Limit value is 128psi at 300rpm  

maximum variance limit between cylinders is 14psi  

so 138 is still above that, but not a huge amount

Yeh got that, thanks.

Something I noticed just looking at the manual again is the fact that you're supposed to use an engine speed sensor, and get a reading at 300rpm - they did not use a speed sensor, nor release fuel pressure (as stated in the manual). Is it possible 138psi is all the guys arm could hold down? If it did hit 300rpm, that's 5 firing's per second. I'm wondering, with a rubber "bung" holding the gauge in - just how reliable that is? If there's dirt around the area the rubber is sealing against - air could escape, maybe?. I'm clutching here I know, just want to bounce some ideas around ;)

See, I was thinking at first fuel pressure would if anything RAISE compression figures. But thinking just a bit more - fuel does not compress. You end up with less air in the cyl. But - that could INCREASE pressure - same force on less air. It's confusing!!! I wish I knew what the **** I was talking about ;) lol

Also, my mechanic did not have a screw-in compression gauge (Allen gauge, whatever the hell they're called) - it was just his arm and a bit of body weight holding the thing in (leaning over car, obviously).

I do trust them, they do this shit all the time and had a new gauge (different to the last time I had my Silvia tested).

I'm wondering if perhaps this isn't really a true reading. Well, I'll rephrase that - I'm HOPING it's an incorrect reading :)

When I get the car, it's stitched up now - I'll take it to a tuner for a baseline test - see what they get as a compression reading, get it dynoed, and get some more results. Worst comes to worst I have to rebuild @ say 5k? Maybe 6k?. In a year or so... hopefully longer. That's BIG outta pocket - but at the same time I get exactly what I want - a new RB26 engine.

Thoughts please :)

yeah thats how I looked at it

You had a rebuild done Duncan? If so, can I ask where? And how long ago?

I'll be honest I'm a little afraid of an "Australian" rebuild. My inclination would be to find uber-rep high priced engine builder and get it done there for peace of mind. Is it much more difficult than rebulding your average NA motor?

Reason I'm asking is my best mate is a mechanic, and that makes life very easy - they do rebuild motors and his old man (partner) was in his younger years a race mechanic and can blueprint motors and stuff - loads of experience, but not with motors such as this.

Should I be trusting them with my RB26DETT?

Aaargh, so many questions, not enough fingers ;)

Bring on the keyboard/mouse implants... lol

:crazy:

Sounds a bit odd the way they did the test without a screw in compression gauge. I can see how it may not be fully sealing the cylinder.

just buy it.. if its the car you want, the paint is good, everything else seems pretty good (gearbox, clutch etc).. at worse its an engine strip one day... gtr engines don't last forever, so it may happen with any you buy. At $28k and you are getting a trade in on your old boys, may as well. If its an 1989/90 just be aware that the value may not hold as well as a newer GTR.. but otherwise, enjoy.

I'm about to get my car compression tested. But is is rocket science or anyone can do it without mistake. This makes the difference between getting CRD to do it for $180 or my cousin to do it for free (just finished his apprenticeship).

Just picked my 32 GTR up a 12/89 model with 101500 on the clock, all cylinders at 165 across the board, so either yours really has more than 100K or its seen a harrrrrd life  :uh-huh: mine had been sitting for a little bit too.

Or, yours has been rebuilt. Maybe with inferior parts that will fly apart after 10 thou....

JUST JOKING! But seriously, it's had a rebuild or a reverse ODO transplant. 165 across the board on a 100,000km engine? It doesn't sound very realistic. Maybe you just scored a freak! Who tested it, by the way - not the seller, right?

Good on ya though, but I've done my research now (lots and lots) and I'm not concerned with the compression anymore. I'd like it to be higher of course!

I'll take it to a reputable tuner and get full comp test, leakdown and dyno. Then I'll have some real info. Kinda moot though. If it dies - it dies. And I buy an N1 motor :P

Sounds a bit odd the way they did the test without a screw in compression gauge. I can see how it may not be fully sealing the cylinder.  

just buy it.. if its the car you want, the paint is good, everything else seems pretty good (gearbox, clutch etc).. at worse its an engine strip one day... gtr engines don't last forever, so it may happen with any you buy. At $28k and you are getting a trade in on your old boys, may as well. If its an 1989/90 just be aware that the value may not hold as well as a newer GTR.. but otherwise, enjoy.

Ah I do love the positive posts :P

Yes, with me no motor will last forever - they never have yet that's for sure. Longest motor I've had is 2.5 years with the Silvia SR20DET. That's including old NA cars, fords, all the cars I've had.

GT-Rs are expensive to own, I've known that going into to it. No point crying if I have to spend a few (or fair few) grand at some point in the future.

I'm very emotional about GT-Rs, so I'm not concerned about holding value. This is my "classic car" not my thrash-n-bash. I'd get a race-only non-registerable Silvy with ridiculous mods for that :)

Like I've said (possibly not on this thread) I'll have a whole new attitude with this car, coming from Silvias. You know how you get old farts with mustangs they polish and love and wank over? Kinda like that, but a decent car instead. I don't care if it's not rare or joe bloggs has one too. It's all about me :)

It's really not that much of an expensive car, so chucking a few bucks at was is to me a cheap supercar - don't sound so bad really does it?

:)

And the gearbox is tighter than a nun! ;p

Andrew

:crazy:

I'm about to get my car compression tested. But is is rocket science or anyone can do it without mistake.  This makes the difference between getting CRD to do it for $180 or my cousin to do it for free (just finished his apprenticeship).

I'd be getting your cousin to do it as long as he has a screw in gauge. I don't trust the "just hold down 140+ psi with one arm leaning over the car" idea. That's a fair bit of force, and hits like a hammer - not a constant push.

No, certainly not rocket science.

EDIT: The hold-in gauge leaves more space in the cylinder. There is more air, and so doesn't compress as much. This IS nit-picking, but a spark plug/screw in gauge will fill a few more CCs. Minor diff, but I know people who have compression tested with a hand-held and then a screw in and read 7 more psi on the screw-in gauge.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • I know why it happened and I’m embarrassed to say but I was testing the polarity of one of the led bulb to see which side was positive with a 12v battery and that’s when it decided to fry hoping I didn’t damage anything else
    • I came here to note that is a zener diode too base on the info there. Based on that, I'd also be suspicious that replacing it, and it's likely to do the same. A lot of use cases will see it used as either voltage protection, or to create a cheap but relatively stable fixed voltage supply. That would mean it has seen more voltage than it should, and has gone into voltage melt down. If there is something else in the circuit dumping out higher than it should voltages, that needs to be found too. It's quite likely they're trying to use the Zener to limit the voltage that is hitting through to the transistor beside it, so what ever goes to the zener is likely a signal, and they're using the transistor in that circuit to amplify it. Especially as it seems they've also got a capacitor across the zener. Looks like there is meant to be something "noisy" to that zener, and what ever it was, had a melt down. Looking at that picture, it also looks like there's some solder joints that really need redoing, and it might be worth having the whole board properly inspected.  Unfortunately, without being able to stick a multimeter on it, and start tracing it all out, I'm pretty much at a loss now to help. I don't even believe I have a climate control board from an R33 around here to pull apart and see if any of the circuit appears similar to give some ideas.
    • Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
×
×
  • Create New...